There are different stages when it comes to learning a new language.
First, you start off with the basics: hello, how are you, my name is Penny, this pie tastes great.
This stuff is pretty much the same in any language.

But when you get past the beginner/intermediate level, you will start to dive deeper into the language and its peculiarities.
And at this point you will hopefully discover how close a language and its culture are related.

A common misconception among language learners is that languages somehow exist in vacuo. It is the idea that you can learn a language without having a certain country in mind.* This is wrong – ask any etymologist. Language and culture are closely connected and interact with each other; it is only because all** human cultures possess a common root that we don’t realize this circumstance from the very beginning.

The culture and history of a country influence certain words and idioms. You can’t use the phrase “Arbeit macht frei” in German without a certain connotation. A country is formed by its politics, its history, its cultural and religious background. Someone from France has a completely different understanding of socialism than someone from Poland or the US. And if a European and an American think of liberalism, they think of two entirely different concepts.

The more you advance in a foreign language, the more you will become aware of those differences. Languages consist to a great extent of figurative speech and allusions. And you need to learn that stuff, too – or otherwise you’ll be lost when a Pole mentions “Kiełbasa wyborcza” (election sausage). And how are you to understand the name of Poland’s most popular newspaper “Gazeta Wyborcza” (The Election Newspaper) when you don’t have the foggiest notion of what happened in Poland during the 1980s?

Learning Polish does not only mean to learn a new language. If you are really determined to do it, you will inevitably learn about the history and culture of the country and its neighbors. Weźmy się do roboty!***

_________________
* This might be one of the reasons why Esperanto never really became prevalent. It is hard to create an artificial language, but it is even harder to create an artificial culture in order to have a context in which the language actually can be used.